The overall aim of the proposed project is to determine the role of endogenous neuropeptides in the control of behavior in the nematode Ascaris. There is a wide diversity of neuropeptides in Ascaris, comprising at least 16 families. The family of FMRFamide-like peptides includes at least 15 members. In the proposed grant period we plan to determine the role of Ascaris FMRFamide-like peptides by determining their site of action at the single cell level. Using specific antibodies we will also identify the individual neurons that contain each of these peptides, thus identifying both halves of the intercellular signaling system mediated by each neuropeptide. We also plan to use several novel strategies to discover new families of neuropeptides; these will include bioassay,an immunoassay that will recognize peptides unrelated to previously identified peptides, and the application of several chemical modifications. Gaining a basic understanding of the Ascaris nervous system is important since Ascaris is a model nematode in which to investigate the control of locomotion in nematodes. The Ascaris motor nervous system is anatomically similar to that of other nematodes, so it is reasonable to assume that this similarity will also apply at the functional level. By studying the mechanisms underlying the activity of the neuromuscular system of Ascaris, and the role of neuropeptide in controlling this activity, general principles applying to other nematodes will be found. This basic understanding of the nematode nervous system will make a contribution to parasite biology, and allow differences in the biology between host and parasite to be identified on food supplies, and the problems they cause as animal and human parasites, especially in tropic and economically less- developed countries, this is an important health-related goal.